Coplanar waveguide (CPW) and slotline are the most widely used uniplanar transmission lines. The use of uniplanar transmission lines allows easy series and shunt devices without via holes and easy mounting of external components, and thus, offers great design flexibility. These characteristics make CPW and slotline important in MIC (Microwave Integrated Circuit) and MMIC (Millimeter Wave Integrated Circuit) design. To fully utilize the advantages of uniplanar structures, broadband transitions of CPW-slotline are necessary. Such CPW-slotline transitions are, for instance, described in WO 97/17738 A1 and the article of C. Ho, L. Fan and K. Chang, “Transmission Line Modeling of CPW-Slotline Transitions and CPW Butterfly Filters”, in IEEE MTT-S Digest, 1994, pp. 1305-1308.
Switches are one of the indispensable devices in microwave and millimeter wave systems, and generally are connected with other components in series. This, however, requires more space for the switches in the system, and also mostly requires additional impedance matching networks which can make system design more complicated.
U.S. Pat. No. 7,605,674 B2 discloses a radiofrequency switch for switching between a transmission signal and a received signal at a signal transmission/reception end in a time division duplexing system. In said RF switch a slotline is divided into a first slotline and a second slotline, and an open-end circuit is provided at each end portion of the first and second slotlines. A first transmission line delivers signals from and to the first slotline, and a second transmission line delivers signals from and to the second slotline. A third transmission line delivers signals from and to the portion of the slotline that separates the first slotline from the second slotline. A variable subopen-end circuit portion includes at least one open-end circuit, which is selectively switched to the first or second slotline according to an external switching control signal.